After the mill

CAD/CAM has become a way of life for some technicians and dental labs, but even labs with little to no CAD/CAM investment have felt the impact from the technology and the material and restoration options it’s made available. Numerous outsource options and workflows are available, ranging from sending a model to be scanned, designed and milled by an outsource partner, to investing in a scanner for in-house design, to buying into a complete system with on-site milling. It comes down to each lab finding what level of integration fits best.

For some labs outsourcing, coping and framework production will provide great efficiencies, for others it might be custom abutment fabrication, while other labs may offer full-contour CAD/CAM crowns to their dentists without investing in a scanner or a mill. Regardless of a lab’s investment, just about every lab should be prepared to finish CAD/CAM restorations.

Not such a big change

DENTSPLY Prosthetics’ Global Programs Manager Veeraraghavan Sundar said a lab first must answer the business question of where CAD/CAM-whether in house or outsourced-will fit in the lab’s workflow because the technology is certainly a part of the future of the industry. Labs may find they increase their efficiency by outsourcing coping and framework production to focus solely on the critical porcelain work dentist clients have come to count on.

“What’s underneath, that is a critical part, but the dentist doesn’t necessarily recognize that,” Sundar said.

This flexibility is one of the big benefits to CAD/CAM technology, added DENTSPLY Prosthetics Product Manager Rebecca Winemiller. While Sundar said labs who outsource any part of design or production will need to adjust to losing a bit of control over the process, Winemiller noted that once outsourced parts are back from the milling center, finishing a restoration will not require major process adjustments.

“They’re building and layering porcelain. They’re staining and glazing. They follow the recommendations for the substructure, but there’s not a lot of extra equipment or extra technique involved,” she said.

In reality, mastering design software and adjusting to in-house milling  requires the biggest learning curves and adjustments for a lab, said Beth Collington, Sales Training/Education Manager at Zahn Dental. Partnering with an outsource center such as Custom Milling Center in Arvada, Colo. is an option that can lessen that curve, but however a lab fits new technology and processes into its operations, Collington said labs that take advantage of CAD/CAM can offer highly esthetic restorations with stable fabrication costs.

“The reason people move away from traditional PFM is for esthetics, because metal can look gray at the margin and there are better esthetic choices where full-contour zirconia is indicated,” she said. “Also metal costs can be expensive based on alloy content.”

Achieving the same esthetics a lab is used to providing requires following the same steps the lab is used to taking. Whether milled or cast, a framework will need to provide the same level of support to the veneering porcelain, Sundar said. When it comes to finishing the restorations, the differences are subtle, and the keys as always are using compatible materials and following manufacturer directions.

“Ceramic surfaces are sensitive to finishing technique, so they need to use a water-cooled handpiece with diamond burs,” Winemiller added. “Ultimately, following the recommended polishing steps and being familiar with that particular product will determine the clinical success of the case.”

Sticking with what works

A lab moving from alloy to zirconia substructures will need a zirconia compatible porcelain. However, finding an entirely new system does not have to be a part of the equation. Most porcelain systems now offer layering porcelain for zirconia and the shades will often compliment and match shading with the corresponding PFM porcelain from the same manufacturer, Collington said, adding that most  Zirconia porcelains should work well with any Zirconia substructure because the material has a stable CTE.

The ability to stay with a familiar porcelain shade system can help minimize the learning curve. For instance, a lab using DENTSPLY’s Ceramco 3 could migrate to Ceramco PFZ, while a lab using Noritake EX-3 could make a similar move to Noritake CZR when transitioning to zirconia substructures. However, Sundar noted that any transition requires attention to detail.

“There’s always going to be a bit of a learning curve,” Sundar said. “I would recommend they be patient and make sure they work through it and learn the particular nuances and workflow of working with that system.”

Finishing touches

That advice also goes for labs making a transition to finishing full-contour milled restorations that will only require the lab to add final stain and glaze effects.
This step can be a tricky one for some labs because there is less they can do to adjust shade, translucency and other esthetic details, Collington said. Because most full-contour translucent zirconias need to be dipped or painted with a coloring solution prior to sintering, labs outsourcing the milling steps need to trust the milling partner to provide the correct shade. Remakes can be costly and frustrating because once sintered, the core color is difficult to change.

That issue is sidestepped with a material such as Pentron Ceramics’ Zirlux FC, which is full contour zirconia manufactured with pigment blended throughout the material. Collington said Zirlux crowns have shade all the way through to the core and can be finished using the Zirlux FC Characterization kit to achieve precise shading and accents.

“It’s going to change the face of full-contour because it’s so easy,” she said.

With much of a full-contour zirconia crown’s color on the surface, a dentist grinding the crown to adjust occlusion can create a white spot, but Collington said Zirlux crowns avoid that problem because the shade is blended throughout. However, dentists should be taught to avoid this problem for more than esthetic reasons, Sundar said. With research showing full-contour zirconia is very kind to opposing dentition when properly polished, labs need to help dentists understand the importance of retaining or restoring that polish when the crowns are seated.

Making the transition

When it comes to figuring out where and how CAD/CAM might fit within a lab’s operations, that is also something that does not need to be done alone. Sundar said DENTSPLY’s technical education department is staffed with CDTs experienced at helping labs move through the process. Custom Milling Center also is staffed with experienced CDTs to support customers new to the process of finishing milled restorations.

This can really involve as little as adding accent shades to a full-contour crown to as much as casting from a milled wax coping. Just about any part of a lab’s workflow can be fit to a CAD/CAM model, it’s just a matter of deciding which one makes the most sense for an individual business.

“It’s not for everybody, but the process is so flexible that labs can choose what level they want to participate at and when,” Sundar said.